An Analytical Approach for Assessment of the Effects of Infill Panels in RC Frames

The use of macro-modeling approaches based on the concept of the equivalent strut for simulating infill panels presents a number of critical aspects, mainly related to the variability of the results from the parameters adopted (for example: width of the strut, non-linear constitutive law under cyclic actions, assignment of strut mechanical properties in multiple strut models). It should also be observed that it is particularly difficult to identify and calibrate the above mentioned quantities, even if the mechanical parameters of the masonry components (mortar and bricks) are known. It is thence highly desirable to define numerical procedures for aimed at this task, in order to reduce the variability of results due to the characteristics of the equivalent strut. In the present paper, the first results of a procedure aimed at the calibration of the macro-models of infill panels are presented. The adopted methodology directly considers the heterogeneity of materials and the texture effects at the micro-scale, exploiting a "Rigid Body and Spring Model"(RSBM), in which the masonry panel is described as a set of unitary cells constituted by rigid blocks and elasto-plastic springs. The non-linear cyclic law of the equivalent strut is then obtained by a simple numerical identification procedure. The approach has been validated on the basis of some reference experimental tests available in the technical literature, by comparing the experimental results and those obtained respectively by RBSM model and the strut model previously calibrated with the proposed procedure.